Ocular tissues synthesize a number of growth factors. As such, several systems has been found that could self- regulate growth and metabolic activity in the retina- pigment epithelium and be involved in eye diseases. These specific growth and differentiating factors can guide development and interactions of individual ocular tissues to form a functional visual system. Studies in this project are focused on an understanding of the molecular biology and molecular genetics of the retina. In this regard, we have cloned and characterized a unique differentiating protein secreted from fetal human pigment epithelial cells, called pigment-epithelial differentiating factor (PEDF), that is "neurotropic" to cultured human retinoblastoma cells and may affect neural retinal development in vivo. This protein also is a potent neuron survival protein in that it promotes neuronal cell survival of cultured brain cells. Along with being a candidate gene in retinal degenerations, the uses of PEDF in neuronal transplant in retina and other central nervous system areas are indicated.